The user interface to computers has continually evolved from teletypes to keyboard and character terminals to the (graphical user interface) GUI which is currently the standard interface for the majority of computer users. This evolution is continuing with sound and 3D graphics increasingly common and 3D sound and virtual reality emerging. It's common thread is an increase in the complexity of the human computer interface achieved by an accompanying is increase in the types of data presented to the user (personal computer) PC applications are taking advantage of this shift and are increasingly relying on the availability of sound and 3D graphics in order to achieve their full potential.
This has resulted in chip and board suppliers offering products with combined functionality designed to handle more than one data type e.g. 2D graphics and sound or 2D and (motion picture experts group) MPEG playback. it is important to note that these products to date use separate functional units for each data type.
More recently, programmable SIMD (Single Instruction Multiple Data) architectures (e.g. Chromatics MPACT) have emerged. These architectures use identical processing elements executing the same instruction to perform the same processing on a number of blocks of data in parallel. This approach works well for data which can be easily partitioned to allow a common function to be performed e.g. block processing in data compression such as MPEG, but are not flexible enough to execute a complete general algorithm which often requires conditional flow control within the data processing.
DSP (digital signal processor) vendors have also sought to address this market with MIMD (Multiple Instruction Multiple Data) devices (e.g. Texas Instruments' TI320C80) which offer the required flexibility to process the varied data types. However since the architecture replicates general purpose DSP cores which retain a far greater degree of flexibility than required for the application, the resulting chip is a high cost device, too high for general PC and consumer use.
CPU (central processing unit) vendors promoting fast RISC CPUs for both general purpose programs and multimedia processing are unable (and do not wish) to compromise their architecture in order to support more than a few multimedia specific instructions and therefore do not achieve the required performance levels at a reasonable cost. As the CPU is also typically being used to run a non-real-time operating system, it is also unable to provide low latency processing.
Dedicated multimedia CPUs (e.g. Philips' Trimedia) using VLIW (very long instruction words) instructions controlling multiple processing units are unable to make efficient use of their processing power because each instruction is dedicated to a single task (and data type) and therefore unable to make optimal use of all the processing units available. For example a VLIW instruction dedicated to a 3D graphics operation is unable to take advantage of hardware designed for MPEG motion estimation. The number of processing units, and therefore scale-ability, is also limited by the VLIW word length.